100 % solution for Passing Cars Task on Codility

PassingCars.js

function solution(A) {
  var zero = 0;
  var count = 0;

  for (var i = 0; i < A.length; i++) {
    if (A[i] == 0) zero++;
    else {
      count += 1 * zero;
      if (count > 1000000000) return -1;
    }
  }

  return count;
}

count += zero without multiply would work too :-)